This invention relates to a process and the apparatus utilized therein for enhancing the tonal quality and details of an optical image, photograph or photographic transparency using electronically controllable techniques.
Various methods have been employed in the past to enhance a photograph. For example, in the exposure stage when taking the photograph, one can sometimes control the lighting to achieve a desired tonal quality in the photograph. This is quite time consuming and does require a complete control of the environment photographed and the subject matter, which at best is rare. Actually, many photographs are taken to capture an event that does not provide the luxury of time for setting up the scene with respect to the surrounding illumination.
In another method, the tonal scale of a black and white photographic image may be modified by changes in the development process. Using color film, the approach becomes almost impossible because the three film layers of red, blue, and green respond differently to changes in development. Changes made to the image in the development process are irreversible.
Other techniques involve modifying the image when the photograph is actually printed from the developed transparency. One advantage of this method is that if a mistake is made such that the results are not those desired, it merely requires that another print be made. If all of the desired information is present in the source transparency, either a positive or a negative, the visual tonal range can be compressed or expanded by using an unsharp or sharp light mask. A mask is normally a copy of the image placed in direct contact with it. A positive mask would increase contrast while a negative mask would decrease contrast. One of the problems encountered in this technique is the alignment of the mask (a greater problem using the sharp mask rather than an unsharp mask). Another method for enhancing a photograph can be employed by manually modifying the light hitting the print. One technique is called "burning in" which allows more light to hit a selected part of the image, and conversely "dodging" which allows less light to hit selected areas of the print. These are done normally with special tools or manually by the printer himself. "Burning in" and "dodging" are not practical for mass production of photographic prints.
One common problem in the production of a photograph is the illumination of different parts of the subject by multiple light sources of different special characteristics. There is no known optical method for correcting an image photographed under these conditions.
The present invention provides an improvement over the techniques discussed above in that the present invention and improved method disclosed herein allows for electronically controllable tonal modification of the final image photographed which can be done accurately and consistently on a mass production basis. The colors and tones at all locations of the projecting surface may be independently modified to achieve the desired enhancement of the source image, and the resultant composite image viewed and reproduced, photographically or otherwise.
The resolution of the enhancement means only affects the quality of enhancement not the resolution of the composite image.